Swept-tone interferers are usually characterized by linear frequency modulations: the instantaneous frequency of the signal sweeps a range of several megahertz (MHz) in a few microseconds, thereby affecting the entire band targeted by the interfering signal. A narrowband system or one or more hops of a frequency-hopped system, which is subjected to this broadband swept-tone interferer, may experience degraded system performance. Furthermore, the fast variations of the instantaneous frequency of swept-tone jammers make the design of estimation and mitigation techniques particularly challenging.
In an effort to mitigate swept-tone interferers, previous approaches developed include adaptive notch filters that can track the instantaneous frequency of the swept tone (see, for example, “Tracking and Mitigating a Jamming Sign al with an Adaptive Notch Filter,” Daniele Borio et al., Inside GNSS, March/April 2014), joint estimation of the parameters of a chirp signal using a least-squares approach (see, for example, “Parameter Estimation of Chirp Signals,” Petar M. Djurić and Steven M. Kay, IEEE Transactions on Acoustics, Speech, and Signal Processing, Vol. 38, No. 12, pp. 2118-2126, December 1990), and tone prediction using an adaptive filter structure to enable cancellation of periodic interference signals (see, for example, the disclosure in U.S. Pat. No. 6,434,233 B1).